Thermoanalytical investigation of Mg(II) compounds containing SCN and heterocyclic N-donor ligands

Abstract

Thermogravimetry (TG), differential thermal analysis (DTA) and other analytical methods have been applied to investigate the thermal behaviour and structure of the compounds Mg(SCN) 2(pic) 2.2H 2O( I), Mg(SCN) 2(ron) 2.3H 2O( II) Mg(SCN) 2(mpc) 2.3H 2O( III) and Mg(SCN) 2(caf) 2.7H 2O ( IV) (where pic, γ-picoline; ron, ronicol; mpc, methyl-3-pyridyl carbamate; and caf, caffeine) in each case. Thermal decomposition of these compounds showed is multi-stage processes. The composition of these complexes, the solid state intermediate as well as the resultant products of thermolysis, have been identified by means of elemental analysis and compleximetric titration. The possible schemes of the decomposition of these complexes are suggested. Heating of these compounds first results in the release of water of crystallization. The loss of the volatile ligands occurs (from the TG curves) in two steps. The final product of the thermal decomposition in each case was MgS. The relative thermal stability of the complexes varied as follows: II< IV< III< I. The ligands (pic, ron, mpc and caf) were coordinated to Mg(II) through the nitrogen atom of the heterocyclic ring. IR data suggest that the SCN group is coordinated to Mg(II) through nitrogen and sulfur in complexes I– IV.